#!/usr/bin/env -S python3 -B

# This script is used to turn one or more of the "patch/BASE/*" branches
# into one or more diffs in the "patches" directory.  Pass the option
# --gen if you want generated files in the diffs.  Pass the name of
# one or more diffs if you want to just update a subset of all the
# diffs.

import os, sys, re, argparse, time, shutil

sys.path = ['packaging'] + sys.path

from pkglib import *

MAKE_GEN_CMDS = [
        './prepare-source'.split(),
        'cd build && if test -f config.status ; then ./config.status ; else ../configure ; fi',
        'make -C build gen'.split(),
        ]
TMP_DIR = "patches.gen"

os.environ['GIT_MERGE_AUTOEDIT'] = 'no'

def main():
    global master_commit, parent_patch, description, completed, last_touch

    if not os.path.isdir(args.patches_dir):
        die(f'No "{args.patches_dir}" directory was found.')
    if not os.path.isdir('.git'):
        die('No ".git" directory present in the current dir.')

    starting_branch, args.base_branch = check_git_state(args.base_branch, not args.skip_check, args.patches_dir)

    master_commit = latest_git_hash(args.base_branch)

    if cmd_txt_chk(['packaging/prep-auto-dir']) == '':
        die('You must setup an auto-build-save dir to use this script.')

    if args.gen:
        if os.path.lexists(TMP_DIR):
            die(f'"{TMP_DIR}" must not exist in the current directory.')
        gen_files = get_gen_files()
        os.mkdir(TMP_DIR, 0o700)
        for cmd in MAKE_GEN_CMDS:
            cmd_chk(cmd)
        cmd_chk(['rsync', '-a', *gen_files, f'{TMP_DIR}/master/'])

    last_touch = int(time.time())

    # Start by finding all patches so that we can load all possible parents.
    patches = sorted(list(get_patch_branches(args.base_branch)))

    parent_patch = { }
    description = { }

    for patch in patches:
        branch = f"patch/{args.base_branch}/{patch}"
        desc = ''
        proc = cmd_pipe(['git', 'diff', '-U1000', f"{args.base_branch}...{branch}", '--', f"PATCH.{patch}"])
        in_diff = False
        for line in proc.stdout:
            if in_diff:
                if not re.match(r'^[ +]', line):
                    continue
                line = line[1:]
                m = re.search(r'patch -p1 <patches/(\S+)\.diff', line)
                if m and m[1] != patch:
                    parpat = parent_patch[patch] = m[1]
                    if not parpat in patches:
                        die(f"Parent of {patch} is not a local branch: {parpat}")
                desc += line
            elif re.match(r'^@@ ', line):
                in_diff = True
        description[patch] = desc
        proc.communicate()

    if args.patch_files: # Limit the list of patches to actually process
        valid_patches = patches
        patches = [ ]
        for fn in args.patch_files:
            name = re.sub(r'\.diff$', '', re.sub(r'.+/', '', fn))
            if name not in valid_patches:
                die(f"Local branch not available for patch: {name}")
            patches.append(name)

    completed = set()

    for patch in patches:
        if patch in completed:
            continue
        if not update_patch(patch):
            break

    if args.gen:
        shutil.rmtree(TMP_DIR)

    while last_touch >= int(time.time()):
        time.sleep(1)
    cmd_chk(['git', 'checkout', starting_branch])
    cmd_chk(['packaging/prep-auto-dir'], discard='output')


def update_patch(patch):
    global last_touch

    completed.add(patch) # Mark it as completed early to short-circuit any (bogus) dependency loops.

    parent = parent_patch.get(patch, None)
    if parent:
        if parent not in completed:
            if not update_patch(parent):
                return 0
        based_on = parent = f"patch/{args.base_branch}/{parent}"
    else:
        parent = args.base_branch
        based_on = master_commit

    print(f"======== {patch} ========")

    while args.gen and last_touch >= int(time.time()):
        time.sleep(1)

    branch = f"patch/{args.base_branch}/{patch}"
    s = cmd_run(['git', 'checkout', branch])
    if s.returncode != 0:
        return 0

    s = cmd_run(['git', 'merge', based_on])
    ok = s.returncode == 0
    skip_shell = False
    if not ok or args.cmd or args.rebuild or args.shell:
        cmd_chk(['packaging/prep-auto-dir'], discard='output')
    if not ok:
        print(f'"git merge {based_on}" incomplete -- please fix.')
        if not run_a_shell(parent, patch):
            return 0
        if not args.rebuild and not args.cmd:
            skip_shell = True
    if args.rebuild:
        if cmd_run(['packaging/smart-rebuild']).returncode != 0:
            if not run_a_shell(parent, patch):
                return 0
            if not args.cmd:
                skip_shell = True
    if args.cmd:
        if cmd_run(args.cmd).returncode != 0:
            if not run_a_shell(parent, patch):
                return 0
            skip_shell = True
    if args.shell and not skip_shell:
        if not run_a_shell(parent, patch):
            return 0

    with open(f"{args.patches_dir}/{patch}.diff", 'w', encoding='utf-8') as fh:
        fh.write(description[patch])
        fh.write(f"\nbased-on: {based_on}\n")

        if args.gen:
            gen_files = get_gen_files()
            for cmd in MAKE_GEN_CMDS:
                cmd_chk(cmd)
            cmd_chk(['rsync', '-a', *gen_files, f"{TMP_DIR}/{patch}/"])
        else:
            gen_files = [ ]
        last_touch = int(time.time())

        proc = cmd_pipe(['git', 'diff', based_on])
        skipping = False
        for line in proc.stdout:
            if skipping:
                if not re.match(r'^diff --git a/', line):
                    continue
                skipping = False
            elif re.match(r'^diff --git a/PATCH', line):
                skipping = True
                continue
            if not re.match(r'^index ', line):
                fh.write(line)
        proc.communicate()

        if args.gen:
            e_tmp_dir = re.escape(TMP_DIR)
            diff_re  = re.compile(r'^(diff -Nurp) %s/[^/]+/(.*?) %s/[^/]+/(.*)' % (e_tmp_dir, e_tmp_dir))
            minus_re = re.compile(r'^\-\-\- %s/[^/]+/([^\t]+)\t.*' % e_tmp_dir)
            plus_re  = re.compile(r'^\+\+\+ %s/[^/]+/([^\t]+)\t.*' % e_tmp_dir)

            if parent == args.base_branch:
                parent_dir = 'master'
            else:
                m = re.search(r'([^/]+)$', parent)
                parent_dir = m[1]

            proc = cmd_pipe(['diff', '-Nurp', f"{TMP_DIR}/{parent_dir}", f"{TMP_DIR}/{patch}"])
            for line in proc.stdout:
                line = diff_re.sub(r'\1 a/\2 b/\3', line)
                line = minus_re.sub(r'--- a/\1', line)
                line =  plus_re.sub(r'+++ b/\1', line)
                fh.write(line)
            proc.communicate()

    return 1


def run_a_shell(parent, patch):
    m = re.search(r'([^/]+)$', parent)
    parent_dir = m[1]
    os.environ['PS1'] = f"[{parent_dir}] {patch}: "

    while True:
        s = cmd_run([os.environ.get('SHELL', '/bin/sh')])
        if s.returncode != 0:
            ans = input("Abort? [n/y] ")
            if re.match(r'^y', ans, flags=re.I):
                return False
            continue
        cur_branch, is_clean, status_txt = check_git_status(0)
        if is_clean:
            break
        print(status_txt, end='')

    cmd_run('rm -f build/*.o build/*/*.o')

    return True


if __name__ == '__main__':
    parser = argparse.ArgumentParser(description="Turn a git branch back into a diff files in the patches dir.", add_help=False)
    parser.add_argument('--branch', '-b', dest='base_branch', metavar='BASE_BRANCH', default='master', help="The branch the patch is based on. Default: master.")
    parser.add_argument('--skip-check', action='store_true', help="Skip the check that ensures starting with a clean branch.")
    parser.add_argument('--shell', '-s', action='store_true', help="Launch a shell for every patch/BASE/* branch updated, not just when a conflict occurs.")
    parser.add_argument('--cmd', '-c', help="Run a command in every patch branch.")
    parser.add_argument('--rebuild', '-r', help="Run the smart-rebuild script in every patch branch.")
    parser.add_argument('--gen', metavar='DIR', nargs='?', const='', help='Include generated files. Optional DIR value overrides the default of using the "patches" dir.')
    parser.add_argument('--patches-dir', '-p', metavar='DIR', default='patches', help="Override the location of the rsync-patches dir. Default: patches.")
    parser.add_argument('patch_files', metavar='patches/DIFF_FILE', nargs='*', help="Specify what patch diff files to process. Default: all of them.")
    parser.add_argument("--help", "-h", action="help", help="Output this help message and exit.")
    args = parser.parse_args()
    if args.gen == '':
        args.gen = args.patches_dir
    elif args.gen is not None:
        args.patches_dir = args.gen
    main()

# vim: sw=4 et ft=python